Eurasia: endemic to the Caspian Sea drainage. Construction projects along the rivers entering the Caspian Sea have had a very negative impact. Very rare now in the Volga river (Ref. 12275). Migrates to uppermost tributaries of Volga (Ref. 59043). Reported to migrate for spawning to the Sura River and its tributaries (the Penza, Aiva, and Inza rivers) as far as Penza Ciry in the 1920s (Ref. 58030).

Biology
Glossary
(e.g. epibenthic)

Non-parasitic (Ref. 59043). Ammocoetes burrow 1-2 cm deep in substrates containing sand, clay, and detritus, in areas with slow current, and at water depths 0.3-22 m; also on surface of substrate among macrophytes and submerged wood. Metamorphosing individuals occur in areas with faster current, devoid of macrophytes, and in deeper water. Adults in rivers and marine waters; in shallow lakes in flood plain of the Volga River delta. Larval life is 3 years in the Volga River Basin and 2-4 years in the Kura River Basin. Ammocoetes feed on diatoms and detritus; feeding activity highest in summer, lowest in the winter. Metamorphosis begins in mid-July in the Volga River (Russian Federation); end of August to early September in the Kura River (Azerbaijan); and October in Iran (Islamic Republic of). Metamorphosing ammocoetes do not feed. Anadromous. Adult life at least 17 months. Indications that adults feed as scavengers or might feed on demersal fish eggs or on some invertebrates; feeding habits still subject of speculation since their teeth are blunt, yet their intestine remains functional and they grow considerably post-metamorphosis. Adults on their spawning run will attach, particularly in the opercular region, to likewise upstream-migrating winter form of brown sea trout (Salmo trutta caspius). Prespawning adults in the Kama River, Russian Federation, serve as a host for unionid glochidia, which attach to its gills. Spawning run is nocturnal; up the Kura River in November-February and Volga River, mid-September-March. Upstream migrants swim near the surface on dark nights and close to the river bottom on moonlit nights. During the day, they stay among stones on the bottom. Max. distance traveled, 1,500 km for larger individuals. Swimming speed, 2-16 km/day. Beginning migration, fat content of adult as high as 34% by body weight, terminating on spawning grounds with as low as 1-2% by body weight, at first concealing themselves amongst stones or burrow into the substrate, and later, swim and periodically break the water’s surface with their heads. Spawning in mid-March to mid-July over sandy and rocky substrate, at water temperatures 15-23 ?C. Spawning grounds along the entire courses of the Volga and Kura rivers from estuaries to the upper reaches historically, and to man-made reservoirs presently. Redds are constructed by both sexes in sand and gravel substrates, usually in shallow waters. Fecundity, 14,000-60,000 eggs/female. Ammocoetes hatch 8-10 days after fertilization at lengths of 0.33-0.42 cm. Three to four days after hatching, yolk sac is almost completely absorbed. Volga River fishery carried out in both the spring and autumn, with over 75% of the catch occurring in autumn. Between 1910 and 1913 inclusively, from 16,900,000 to 33,400,000 Caspian Lamprey were harvested annually. Kura River fishery catches compiled in five-year increments from 1881 to 1935 with lowest record of 11,000 lamprey for the period 1891-1895 and highest of 612,000 lamprey for the period 1911-1915; 213,000 annual lamprey catch in 1936 and 304,000 in 1937; lipid content is 30.3% of the body weight. Prior to 1868, the catch was dried and used as a substitute for candles, and after 1868, it was harvested as food for humans. The caloric value for Caspian Lamprey is 3.4 kcal/g wet weight. Water regulation projects on the Volga and Kura rivers with deleterious effects on the abundance of Caspian Lamprey, preventing access to areas above the Volgograd and Mingechaur reservoirs, respectively, that it is no longer considered a commercially important species. There are reports of intoxication through eating this species (Ref. 89241).

The nest is dug by either the male or the female. They attach themselves to stones before mating. Females die immediately after releasing their eggs, but males survive until spermatogenesis ceases and can mate with more than one female (Ref. 12275). Ammocoete stage lasts 2-4 years in freshwater after which metamorphosed juveniles migrate to the sea (Ref. 59043). In lower Volga, adults may feed one or two summers before breeding (Ref. 59043). These adults may begin to migrate to rivers in autumn and winter, usually from October to February, unstopped by ice flow in Volga (Ref. 59043).